Effect of calcium-binding protein regucalcin on hepatic protein synthesis: inhibition of aminoacyl-tRNA synthetase activity.
The effect of regucalcin, a calcium-binding protein isolated from rat liver cytosol, on in vitro protein synthesis in the 5500 g supernatant fraction of rat liver homogenate was investigated. Addition of Ca2+ up to 5.0 microM in the reaction mixture caused a significant decrease in protein synthesis. This decrease was saturated at 10 microM Ca2+. The Ca2+ effect was not reversed by the presence of regucalcin (2.0 microM); the protein caused a remarkable decrease in hepatic protein synthesis, and it enhanced significantly the Ca2+ effect. Meanwhile, calmodulin (2.5-20 micrograms/ml), a calcium-binding protein, did not have an appreciable effect on the Ca2+ (10 microM)-induced decrease in hepatic protein synthesis. [3H]Leucyl-tRNA synthetase activity in the 105000 g supernatant fraction (cytosol) of liver homogenate was markedly decreased by addition of Ca2+ (1.0-50 microM). This decrease was not reversed by the presence of regucalcin (2.0 microM); the protein (1.0-2.0 microM) caused a remarkable decrease in the enzyme activity. The present results suggest that regucalcin can regulate protein synthesis in liver cells.
Yamaguchi
M
M
Department of Environmental Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, Japan.
Mori
S
S
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000494:pharmacology*; D002265:Carboxylic Ester Hydrolases; D003600:Cytosol / Q000201:enzymology; D047908:Intracellular Signaling Peptides and Proteins; D007935:Leucine-tRNA Ligase / Q000037:antagonists & inhibitors*; D008099:Liver / Q000201:enzymology* / Q000378:metabolism; D008297:Male; D014176:Protein Biosynthesis; D011817:Rabbits; D051381:Rats; D011919:Rats, Inbred Strains; D015238:Sulfotransferases
D002135:Calcium-Binding Proteins; D047908:Intracellular Signaling Peptides and Proteins; D015238:Sulfotransferases; C028152:alcohol sulfotransferase; D002265:Carboxylic Ester Hydrolases; C513325:Rgn protein, rat; D007935:Leucine-tRNA Ligase; D002118:Calcium